If you post something to the list and it doesn’t show up, you can confirm if it was delivered or not by checking the 3D-PRO archives.
Why didn’t I receive a copy of my post?
If you use Gmail to post to the list, then you will not receive a copy of your posts because it’s a Gmail thing. However, you can change your list preferences to receive an acknowledgment whenever messages you send to the list are distributed.
If you really want to receive a copy of your post, then you can subscribe a second address to the list and post from one and receive messages at the other.